Grinding wheel speed control



Aug. 25., 1942. Q C, ALVQRD 2,294,153

GRNDING WHEEL-SPEED CONTROL' l Filed Oct.. 23, 1941 ZfSheets-Sheet lCHER/ 55 CA V0/QD c. c. ALvoRD 2,235,631 GRINDING WHEEL-SPEED .CONTROLAug. 25, 1942.

,Filed oct. 2s, 1941 2 sheets-ghe z 7. I 'umg LHHRLESCAILQVURD ua-m.,

Patented Aug.` 25, 1942 GRINDING WHEEL SPEED CONTROL Charles C. Alvord,Worcester, Mass., assignor to Norton Company, Worcester, Mass., acorporation of Massachusetts Application october 2s, 1941, serial No.416,158

6 Claims.

eral speed of the wheel may be maintained as it wears away. Anotherobject of the invention is to provide a motor driven mechanism fordriving a grinding wheel at a substantially constant peripheral speed. Afurther object of the invention is to provide a grinding wheel speedregulating mechanism whereby a variable speed motor driven mechanism isautomatically adjusted in timed relation with adjustment of the grinding`Wheel guard whereby a constant peripheral speed may be maintained asthe wheel decreases in size due to wheel wear. Other objects ,will be inpart obvious or in part pointed out hereinafter. v

The invention accordingly consists in the fea,- tures of construction,combinations of elements, and arrangements of parts, as will beexemplified in the structure to be hereinafter described, and the scopeof the application of which will be indicated in the following claims.

In the accompanying drawings in which is shown one of various possibleembodiments of the mechanical features of the invention:

Fig. 1fis an end elevation of a portion of a cylindrical grindingmachine embodying this invention;

Fig. 2 is a fragmentary front elevation, on an enlarged scale, of thegrinding wheel slide unit shown in Fig. 1;

Fig. 3 is a fragmentary left-hand elevation of the grinding wheel slideunit;

Fig.' 4 is a fragmentary cross-sectional view, taken approximately onthe line 4-'4 of Fig. 3,

closed by awheel guard I6 which is adjustably supported on the wheelslide II and serves as a safety medium in case of grinding wheelbreakage. Only the front portion of the wheel guard adjacent to the workpiece ls open.

'I'he wheel guard I6 is arranged so that it may be adjusted transverselyrelative to the wheel slide II so as to maintain the front open edge orlip Il of the guard I6' in close proximity to the periphery of thegrinding wheel I5. A slide member I8 is formed integral with or xedlymounted to the guard I6. A slide member I9 is fixedly mounted on theright-hand side face of the wheel slide II (Fig. 2). Antifrictonslideways are provided comprising a pair of spaced rows of balls 20 and2I which are interposed between the slide members I8 and I9. The lowerportion of the slide member I8 is provided with a slide surface matinglwith a correspondingly shaped angular slide surface l22 formed on theslide member I9 (Fig. 2). It will be readily apparent from the foregoingdisclosure that the slide I6 may be readily and easily adjustedtransversely relative to the wheel slide I I on the slideways abovedescribed to maintain the wheel guard lip I 'I in the desiredrelationship with the periphery of the grinding wheel I5 as it wearsaway. A clamping screw 23 is screw threaded through a portion oftheslide member I8 and is arranged through the slide which supports thegrinding wheel guard; and

Fig. 5 is an electric wiring diagram of the wheel driving mechanism.

A grinding machine hasbeen illustrated in the drawings comprising a baseI0 which supports a transversely movable grinding wheel slide II on aV-way I2 and a flat way I3formed on the upper surface of the base I0.The Wheel slide II- serves as a rotatable support for a grinding wheelspindle I4 which is journalled in bearings (not shown) carried by thewheel slide II. A grinding wheel I5 is mounted on one end ofthe toengage a surface 24 on the slide member I9 to facilitate locking theslide I8 and the wheel guard I6 in the desired adjusted position.

The wheel spindle I4 and the grinding wheel I5 are preferablyelectrically driven by means of a variable speed electric motor 3 0which is mounted on the upper portion of the wheel slide Il. Amulti-V-groove pulley 3| is mounted on the end of a motor shaft 32. Thepulley3I is connected by multiple V-belts 33 with a multi- V-groovepulley 34 which is mounted on the end of the wheel spindle I4.

A rheostat 35 is provided for adjusting the speed of the motor 30. Asillustrated in the wiring diagram (Fig. 5), power is supplied from asuitable source, such as indicated by the power lines 36. A push buttonswitch 3l is provided for opening and closing the circuit tonstop andstart the motor 30 and thereby to control the stopping and starting ofthe rotation of the grinding wheel I5 as desired. Byradjusting a,rheostat control arm 38, the speed of the motor 30 may -be varied. 'I'hecontrol arm 38 illustrated diagrammatically in Fig. 5 is mounted on arheostat sha'ft 39.

In order to attain one object of the invention,

wheel spindle I4. The grinding wheel I5 is en- 55 a suitable controlmechanism is provided whereby the peripheral speed of the grinding wheelI may be maintained at a substantially constant rate as the grindingwheel I5 wears away during grinding. In the preferred form, the rheostat35 is mounted on the wheel guard I6 and is -arranged so that when thewheel guard IB is adjusted transversely to maintain the lip I'I in closeproximity to the operative face of the grinding wheel, the speed of thedriving -motor 30 will be automatically adjusted successively toincrease the peripheral speed of the Wheel as it is reduced in size. Y

I A cam shaped member 40 yis mounted on the outer end of therheostatjcontrol shaft 39. A flexible cable 4I such as, for example, anaircraft control cable, wraps around the periphery of the cam 40 and isclampedin position thereon at one point by means of a clamping block 42(Fig. 2). 'I'he opposite ends of the cable 4I are fastened to brackets43 and 44 (Fig. 1) which are flxedly mounted on the upper surface of thewheel slide II. The cam-shaped member 40 is designed and shaped so thata desired and predetermined rotary or angular adjustment will beimparted to the rheostat 35 which is not directly proportional to thelinear adjustment of. the wheel guard I6 to maintain a substantiallyperipherrl speed of the grinding Wheel I5 as it wears away duringgrinding.

It will be readily apparent from the foregoing disclosure that when thewheel guard I6 is adjusted transversely, the rheostat 35 being fixedly-mounted thereon moves transversely. The cable 4I, the opposite ends ofwhich are fixed relative to the wheel slide II, will then produce arotary motion to the cam 40 which in turn will impart a rotaryadjustment to the armature control arm 38 (Fig. 5) automatically toadvance or increase the speed of the motor 30 as the wheel guard I6 isadjusted transversely to compensate for wheel wear. Similarly, if thewheel guard is moved in the opposite direction such as. for example,when it is desired to replace a worn-out wheel with a new wheel, therheostat control cam 40 and control arm 38 will be rotated in theopposite direction to decrease the speed of the motor for the new largerdiameter wheel.

The operation of-this improved grinding wheel speed control mechanismwill be readily appar'- ent from the foregoing disclosure. The flexible`cable 4I is maintained in a taut condition by the clamping members 43and 44. After a grinding wheel I5 has been mounted in operative positionWithin the wheel guard I6, the wheel guard I6 may -be adjustedtransversely by loosening the clamping screw 23 and manually adjustingthe position of the guard IS so that the lip I1 is in close proximity tothe operative peripheral surface of the grinding wheel. As the wheelguard I6 is adjusted transversely, a rotary motion is imparted throughthe cable 4I and cam 40 to turn the rheostat control arm 38 so as todeg-:1H crease the speed of the driving motor 30 to main- 1 tain asubstantially constant peripheral speed" vennen, it is to Vbe understoodthat an metter hereinbefore set forth or shown in the accompanyingdrawings is to be interpreted as illustrativeand not in a limitingsense.

I claim:

1. In a grinding machine having a transversely movable Wheel slide, arotatable grinding wheel thereon, a wheel guard surrounding saidgrinding wheel, manually operable means to adjust said wheel guardtransversely relative to said grinding wheel, a variable speed electricmotor to rotate said wheel, and a speed control mechanism thereforincluding a rheostat supported on said wheel guard, a rotatable controlshaft for said rheostat, a cam shaped member on said shaft to actuatesaid rheostat, and operative connections between said cam and wheelslide whereby said rheostat is wautomatically adjusted by transverseadjustment of the wheel guard so as to maintain a substantially constantperipheral speed of the grinding wheel as it wears away.

2. In a grinding machine having a transversely movable wheel slide, arotatable grinding wheel thereon, a wheel guard surrounding saidgrinding Wheel, manually operable means to adjust said wheel guardtransversely relative to said grinding wheel, a variable speed electricmotor to rotate said wheel, and a speed control mechanism thereforincluding a rheostat, a rotatable control shaft for said rheostat, acamshaped member on said shaft to actuate said rheostat, and a flexibletape surrounding said cam, said rheostat and said tape being connectedwith the wheel guard and wheel slide respectively whereby said rheostatis automatically adjusted by transverse adjustment of the wheel guard,said cam-shaped member being so shaped as to maintain a substantiallyconstant peripheral speed of the grinding wheel as it wears away.

3. In a grinding machine having a transversely movable wheel slide, arotatable grinding wheel thereon, a wheel guard surrounding saidgrinding wheel, a transverse slide interposed between said wheel guardand wheel slide whereby the guard may be adjusted transversely as thegrinding wheel wears away, a variable speed electric motor on said slidetb rotate said grinding wheel, and a speed control mechanism thereforincluding a rheostat supported on said wheel guard, a rotatable controlshaft for said rheostat, a cam on said shaft to actuate said rheostat,and operative connections including a exible tape which surrounds saidcam and has its opposite ends fixed to said wheel slide whereby saidrheostat is automatically adjusted by transverse adjustment of the wheelguard to maintain a substantially constant peripheral speed of thegrinding wheel as it wears away.

4. In a grinding machine having a transversely movable wheel slide, arotatable grinding wheel thereon, a member movable toward or from theperipheral surface of said wheel, a variable speed electric motor torotate said wheel, a speed control mechanism therefor including arheostat, a rotatable control shaft for said rheostat an'd operativeconnections including a rotatable cam on said shaft between said memberand rheostat Whereby'movement of said member actuates said rheostat,said cam being so shaped and arranged that the angular adjustment ofsaid rheostat ls not directly proportional to the linear adjustment ofthe wheel guard so as to maintain a substantially constant peripheralspeed of the grinding wheel as it wears away.

5. In a grinding machine having a transversely movable wheel slide, arotatable grinding wheel thereon, a wheel'guard surrounding saidgrinding wheel, a transverseslide interposed between said wheel guardand wheel slide to facilitate a transverse adjustment of the wheel guardas the grinding wheel wears away, a variable speed electric motor torotate saidgrinding wheel, and a speed control mechanism thereforincluding a. rheostat and a flexible tape to actuate the same one ofwhich is supported on the wheely guard and the other on the wheel slidewhereby said rheostat is automatically adjusted -by transverseadjustment of the wheel guard to maintain a substantially vconstantperipheral speed of the grinding wheel as it wears away.

6. In a grinding machine having a transversely movable wheel slide, arotatable grinding wheel thereon, a wheel guard surrounding saidgrinding wheel, a transversel slide interposed between said wheel guardand wheel slide to facilitate a transverse adjustment of the wheel guardas the grinding wheel wears away. a variable speed electric motor onsaid slide to rotate said grinding wheel. and a speed control mechanismtherefor including a rheostat supported on said wheel guard, a cam toactuate said rheo'- stat, and a flexible tape which surrounds said camand has its opposite ends xed to the wheel guard whereby said rheostatis automatically ad justed by transverse adjustment of the wheel guardto maintain a substantially constant peripheral speed of the grindingwheel as it wears away. f

CHARLES C. ALVORD.

